Article Type : Research Article
Authors : Ashfaq S and Khan NT
Keywords : Biopesticides; Biofertilizers; Rhizobacteria; Endosphere
Microbial biotechnology plays a crucial
role in sustainable agriculture by harnessing beneficial microorganisms for
various agricultural applications. This review explores the diverse roles of
microbes in agriculture, focusing on their use as biofertilizers and
biopesticides. Key microbial groups such as Plant Growth-Promoting
Rhizobacteria (PGPR) and fungal biocontrol agents are highlighted for their
contributions to enhancing crop nutrition, combating pests and diseases, and
promoting environmental sustainability. The interaction dynamics within the
plant microbiome, including the rhizosphere and endosphere, are also discussed,
emphasizing their impact on plant health and productivity under changing
climatic conditions.
A rapidly expanding area of biological sciences
called biotechnology has several uses in sustainable agriculture. In biological
sciences, it entails employing genetic engineering to change living things or
their components to produce useful products for various uses. The world's
expanding population will significantly strain food production and agriculture
by the end of 2033. In order to meet the rising demand for food, this offers a
difficulty. A rapidly expanding area of biological sciences called biotechnology
has several uses in sustainable agriculture. In biological sciences, it entails
employing genetic engineering to change living things or their components to
produce useful products for various uses. In order to meet the rising demand
for food, this offers a difficulty. Experts like Mostafiz, Rahman & Rahman
[1] and Barea [2] predict that by 2050, the demand for agricultural products
will have increased by at least 70%.[1] As more people become aware of the
significance of food security, this understanding of the necessity for
sustainable agriculture techniques will grow increasingly pronounced. Microbial
biotechnology is essential for developing agricultural science in a number of
areas, including nutrition, food security, and food safety. The basis for
biotechnology research, technology development, and the production of new goods
is genetic material derived from plants, animals, and microbes. By locating,
isolating, cloning, and transferring desirable genes between species,
biotechnology technologies have transformed breeding and rendered outdated the
classic Mendelian population conceptions. Identifying genetic variants,
comprehending how genes work, and improving transgenic organisms with
particular advantageous features are the ultimate goals of biotechnology [3].
Globally, agricultural methods are used to achieve sustainable economic and
environmental growth while protecting the environment. The junction of the
economy and the environment (agroecology), environmental consciousness, and
living standards are key components of the idea of "sustainable
development." Developing effective strategies to reduce the negative
consequences of environmental change, manage pests and illnesses, and recycle
nutrients for sustainability, stressors are essential. For ecological and
economic sustainability, controlling the microbiome of plant roots is crucial
[2]. Agriculture biotechnology, general microbiology, and microbial ecology are
all connected by agricultural microbiology. In both natural and agricultural ecosystems,
it focuses on comprehending how microorganisms are distributed across plants,
animals, and soil conditions [4]. Recombinant DNA technology is used to
artificially insert genes into the genetic makeup of transgenic plants. These
genes may originate from unrelated creatures like bacteria or animals as well
as from members of the same or other species [5].Various advantages of
genetically modified crops include delayed ripening for longer shelf life,
resistance to pests and diseases to use fewer pesticides, resistance to fungi
and viruses, and tolerance to herbicides for better weed control [6,7]. By
minimizing dependency on agrochemicals, notably pesticides, microbial
biotechnology supports sustainable agriculture. It does this by introducing
genes into attractive plant kinds that offer tolerance or resistance to biotic
and abiotic stressors. Improved pest and disease resistance, increased
resiliency to environmental pressures, bioremediation of dirty soils, higher
production, and better nutrient uptake are only a few effects of biotechnology
on sustainable agriculture. The employment of environmentally benign symbiotic
microorganisms in place of hazardous fertilizers and pesticides is one
promising method for sustainable agriculture. These bacteria have the ability
to improve crop nutrition, defend against viruses and pests, and lessen the
consequences of pollution and climate change. Natural resource management,
environmental concerns, and public policy difficulties are just a few of the
many facets that make up agriculture. It uses a variety of techniques [8].
In the approaching decades, utilizing the
advantageous microorganisms in sustainable crop production will become a key
priority. The most biodiverse ecosystem on Earth is thought to exist in the
soil matrix, which serves as a main repository for microorganisms that interact
with plants. This environment's critical processes, which especially affect
plant health, are controlled by the soil microbiome. The ability of the
microbiome to give nutrients (phosphorus solubilization and nitrogen fixation),
enhance nutrient uptake from the soil, and promote plant protection are just a
few of the roles that have been attributed to it in tight relationships with
plants [9]. The natural soil microflora, which contains a variety of beneficial
bacteria and fungi, including the arbuscular mycorrhizal fungus known as
plant-growth-promoting rhizobacteria (PGPR), is what organic farming depends on
the most [10,11]. The ability of beneficial microbes to digest phosphorus for
their own needs which is therefore available in sufficient amounts as its
soluble form in soil is one of their main advantages [12]. It has been
documented that the solubilization process is actively carried out by the
bacteria Bacillus, Pseudomonas, Micrococcus, Flavobacterium, Fusarium,
Sclerotium, Aspergillus, and Penicillium [13]. The main factors limiting the
productivity of the crops are biotic and abiotic stressors [14]. For the
purpose of improving crops under stress, many modern scientific technologies
have been broadly linked, and the role of PGPRs as bioprotectants has emerged
as being of particular significance in this regard [15].
Microorganisms, for example, can help and control
nutrient availability and acquisition and promote stress tolerance, which can
have an impact on agricultural output. The plant microbiome's species variety
and microbial community richness, as well as the variables influencing it and
its functioning, remain mostly unknown. The significance of this topic is
Microbiome of the rhizosphere and sustainable agriculture. In recent years,
there have been an increasing number of scholarly articles on this subject, as
shown by studies concentrating on unique plant niches and how they modify their
specific microbial populations. Understanding the key factors that influence
the composition of the plant microbiome, which is a dynamic and adaptable part
of the host, is crucial to changes in environmental (biotic and abiotic)
conditions. Recent research has focused on different components of the plant
microbiome independently in order to comprehend the variables that affect its
assembly and the dynamics from a phylogenetic and functional perspective. The
so-called rhizosphere, endosphere, and phyllosphere are three significant
compartments where microbial cells can establish and grow [16]. Various
significant crop species and their natural relatives have not yet been
investigated for their associated bacterial communities, despite the fact that
the plant microbiome is thought to be a vast treasure trove of microbial
variety. Outbreaks have been documented to better comprehend the importance of
the plant-associated microbiome in the protection of pathogens [17,18]. The
development of a thorough understanding of the mechanisms underpinning
plant-microbe interactions in the rhizosphere has been hampered by the absence
of an adequate technique. The main difficulties stem from the requirement to
profile an amazing group of processes where the diverse and large microbial
communities are mostly made up of uncultivable microorganisms [19]. These
molecular-based methodologies are crucial for determining how stresses caused
by biotic and abiotic stress factors affect soil microbiome diversity and
plant-microbe interactions in the context of current climate change. A greater
knowledge of the interactions between plants and their microbiomes would enable
soil bacteria to better relieve agricultural stress. Numerous stressors, such
as salt, drought, nutrient deficiency, pollution, diseases, and pests, among
others, can change how plants and microbes interact in the rhizosphere [20].
Researchers found that the structure of plant roots in soil can be affected by
the presence of even little amounts of water. This discovery creates new
opportunities for improving water and nutrient aging for significant food
crops. The extent of root branching affects how effectively crops absorb water
and absorb nutrients. Therefore, it is crucial to comprehend how root branching
is regulated [21].
The majority of the other species that are connected
to plants are bacteria. These include the rhizosphere, soil microorganisms
connected to subterranean plants, endophytes within plants, and epiphytes on
plant surfaces. Organs and soil interfaces for sustainable agriculture using
biotechnology. Agriculture places a special emphasis on the symbiosis between legume
plants and soil-dwelling rhizobia, and more study has focused on characterizing
the molecular processes that produce species-specific cooperation [22].
Host-specific flavonoids that are secreted in the root exudates influence
interactions between legumes and rhizobia. Numerous rhizosphere bacteria have
the ability to activate plant defense mechanisms by triggering a systemic
response in plants. Induced systemic resistance, or ISR, is the term used to
describe signaling pathways that result in increased host pathogen resistance
after exposure to nonpathogenic root zone microorganisms [23,24].
ISR has been demonstrated to be induced by a number
of bacteria, including Bacillus species, which have been utilized to examine
advantageous effects under abiotic stress settings. Bacterial endophytes, which
are used to improve plant agronomic characteristics and biologically control a
variety of plant diseases, may be of particular interest because they have the
benefit of being relatively protected from the competitive soil environment. In
addition, they frequently grow in the same plant tissue where bacterial plant
pathogens are discovered.
Types of Root-Associated
Microorganisms
The
saprophytic or symbiotic relationships between the plant and the prokaryotic
bacteria and eukaryotic fungi have the potential to be harmful or advantageous
depending on their trophic/living behaviors. A small subset of these
microorganisms, referred to as "endophytes," is able to penetrate and
reside within plant tissues, while the great majority of them remain in the
rhizospheric soil or rhizoplane [25]. It is acknowledged that soil bacteria are
an important part of the many interrelated elements that contribute to the
environmental quality needed for a sustained, healthy food supply. The
rhizodeposition pools are what draw microbes to and keep them in rhizosphere
microhabitats [16]. There are many different types of organisms in the soil
microbiome, but studies on the soil microbiome have focused primarily on
bacteria, fungus, and archaea.
Beneficial Rhizosphere
Microorganisms
PGPR, antagonists of plant diseases, or decomposers of organic matter (detritus), beneficial saprophytic rhizosphere bacteria improve plant performance [26]. The biological control of plant diseases and nitrogen cycling are just a couple of the important ecosystem processes that the PGPR are known to take part in [27], N2-fixing bacteria and multipurpose arbuscular mycorrhizal (AM) fungi are examples of beneficial plant mutualistic symbionts [28]. Rhizobia, a collective word for bacteria from several genera, are able to fix N2 in mutualistic symbiosis with legume plants [29]. Nitrogen-fixing microorganisms turn atmospheric nitrogen to ammonia, which is then changed into forms that plants may use (ammonia and nitrate) [30] (Figures 1-2). A vast group of frequently unidentified or ill-defined microorganisms that interact well with plants and in soils are known as agriculturally relevant microfloras [31].The majority of the other species that are connected to plants are bacteria. These include the rhizosphere, soil microorganisms connected to subterranean plants, endophytes within plants, and epiphytes on plant surfaces. Organs and soil interfaces for sustainable agriculture using biotechnology. Agriculture places a special emphasis on the symbiosis between legume plants and soil-dwelling rhizobia, and more study has focused on characterizing the molecular processes that produce species-specific cooperation [22]. Host-specific flavonoids that are secreted in the root exudates influence interactions between legumes and rhizobia. Numerous rhizosphere bacteria have the ability to activate plant defense mechanisms by triggering a systemic response in plants. Induced systemic resistance, or ISR, is the term used to describe signaling pathways that result in increased host pathogen resistance after exposure to nonpathogenic root zone microorganisms [23,24].
ISR has been demonstrated to be induced by a number
of bacteria, including Bacillus species, which have been utilized to examine
advantageous effects under abiotic stress settings. Bacterial endophytes, which
are used to improve plant agronomic characteristics and biologically control a
variety of plant diseases, may be of particular interest because they have the
benefit of being relatively protected from the competitive soil environment. In
addition, they frequently grow in the same plant tissue where bacterial plant
pathogens are discovered.
Types of Root-Associated
Microorganisms
The
saprophytic or symbiotic relationships between the plant and the prokaryotic
bacteria and eukaryotic fungi have the potential to be harmful or advantageous
depending on their trophic/living behaviors. A small subset of these
microorganisms, referred to as "endophytes," is able to penetrate and
reside within plant tissues, while the great majority of them remain in the
rhizospheric soil or rhizoplane [25]. It is acknowledged that soil bacteria are
an important part of the many interrelated elements that contribute to the
environmental quality needed for a sustained, healthy food supply. The
rhizodeposition pools are what draw microbes to and keep them in rhizosphere
microhabitats [16]. There are many different types of organisms in the soil
microbiome, but studies on the soil microbiome have focused primarily on
bacteria, fungus, and archaea.
Beneficial Rhizosphere
Microorganisms
PGPR, antagonists of plant diseases, or decomposers of organic matter (detritus), beneficial saprophytic rhizosphere bacteria improve plant performance [26]. The biological control of plant diseases and nitrogen cycling are just a couple of the important ecosystem processes that the PGPR are known to take part in [27], N2-fixing bacteria and multipurpose arbuscular mycorrhizal (AM) fungi are examples of beneficial plant mutualistic symbionts [28]. Rhizobia, a collective word for bacteria from several genera, are able to fix N2 in mutualistic symbiosis with legume plants [29]. Nitrogen-fixing microorganisms turn atmospheric nitrogen to ammonia, which is then changed into forms that plants may use (ammonia and nitrate) [30] (Figures 1-2). A vast group of frequently unidentified or ill-defined microorganisms that interact well with plants and in soils are known as agriculturally relevant microfloras [31].
Application of
High-Quality Microbial Inoculants
A
thorough analysis of the formulation and practical views of inoculants
technology for PGPR was recently published by Bashan, de-Bashan, Prabhu, and
Hernandez [45]. They suggest several major research goals for developing
delivery methods for PGPR and rhizobia. The following requirements must be met
for the successful application of microbial inoculants in agriculture: (1)
strengthen the scientific and technological foundations of inoculum production
and application; (2) develop specific normative for each type of inoculant and
its application, whether to seeds, soil, or a transplanted plant that has
already been microbeized; (3) establish quality-control protocols; (4) reduce
the fluctuation of field results; and (5) spread knowledge by outlining benefits
and drawbacks for society.
Seed Treatments for
Sustainable Agriculture
Agricultural
Seed Treatments for Sustainability 90% of food crops are grown from seed,
making seed an essential component of sustainable growth in agricultural
production. If not promptly dealt with, seed-borne, early-season illnesses and
insects have devastating effects. In modern agriculture, the focus is on
producing more with less land, water, and labor. In order to combat plant
pathogens, traditional environmentally friendly disease management techniques
like sanitation, crop rotation, mixed cropping, adjusting the date of sowing,
fallowing, summer plowing, green manuring composting, etc. are currently being
reevaluated as a part of integrated pest management [46].
Encourage Beneficial Microbe Establishment at Rhizosphere
Gaining
a biased rhizosphere undoubtedly creates new prospects for agricultural
advancements based on utilizing advantageous microbial services to reduce
pesticide inputs and so achieve sustainable environmental and economic goals
[47].
1.
Using agricultural practices to harness the microbial communities in the
rhizosphere.
2.
Understanding how plants influence the rhizosphere's microbial community
structure.
3.
The idea or practice of the "biased rhizosphere".
In order to ascertain whether the rhizosphere may be manipulated (biased) to strengthen beneficial organisms while preventing the presence of diseases, a number of approaches are currently being pursued. Due to the considerable gaps in our understanding, the objective research themes present numerous challenges.
Figure 1: Rhizospheric soil.
Figure
2:
Nitrogen-fixing microorganisms
s |
Microorganisms |
Target Pest |
Mode of Action |
Bactericide |
Agrobacterium radiobacter |
Crown gall (Agrobacterium tumefaciens) |
Antagonist and antibiosis |
Bacillus polymyxa |
Crown gall |
Antagonist and antibiosis | |
Bacillus sphaericus |
Crown gall |
Antagonist and antibiosis | |
Bacillus subtilis |
Bacterial pathogen |
Colonizes on plant root
and competes | |
Pseudomonas fluorescens |
Several bacterial diseases such as frost-forming bacteria |
Crowds out and controls the growth of plant
pathogens | |
Fungicide |
Bacillus subtilis |
Soil foliage, fungal pathogens such as
Rhizoctonia, Fusarium, Aspergillus, and others |
Colonizes on plant
root and competes and antibiosis |
Pseudomonas syringae |
Postharvest disease |
Utilize seed exudates, produce a wide spectrum of bioactive metabolites | |
Bacillus pumilus |
Seedling disease |
Colonizes on plant root
and competes and antibiosis | |
Streptomyces |
Fungi-causing damping off, stem,
and crown rots |
Mycoparasitic, antagonist, and antibiosis | |
Pseudomonas fluorescens |
Plant soil-borne diseases, fireblight |
Utilize seed and root exudates and colonize, produce a wide spectrum
of bioactive metabolites | |
Trichoderma viride/ harzianum |
Soil-borne fungal disease |
Mycoparasitic, antagonist, and antibiosis | |
Burkholderia cepacia |
Fungal pathogens |
Controls fungi
via seed treatment | |
Gliocladium catenulatum |
Seed-borne and soil- borne diseases |
Enzymatic mechanism | |
Candida oleophila |
Postharvest
pathogens |
Colonization of diseased tissues |
One
of the main issues facing the world today is climate change, which has an
impact on life on Earth. The general shape, functioning, and photosynthesis
(the assimilation of carbon) of plant specimens as well as their interactions
are typically impacted by climate change [48]. A rise in atmospheric carbon
dioxide (CO2) lowers the nitrogen content of crops, which may delay the onset
of many pests and illnesses and alter the makeup of the weed flora that grows
alongside the crops [49]. Agriculture suffers a variety of difficulties as a
result of the excessive and illegal usage of chemical fertilizers. It is well
recognized that a significant portion of the vital, naturally occurring micro-
and macronutrients in soil are destroyed by synthetic fertilizers [50]. Changes
in plant physiology and root exudation are anticipated to result from changes
in environmental conditions brought on by a changing climate. To advance our
understanding of native biodiversity and microbial community structure in the
context of a changing climate, research is crucial [51].
Biofertilizers
A
preparation containing active or dormant cells of effective strains of
nitrogen-fixing, phosphate-solubilizing, and cellulytic microorganisms, among
others, is referred to as a biofertilizer. Biofertilizers, in contrast to
chemical fertilizers, are living microorganisms that aid plants in accessing
the nutrient availability in the rhizosphere but do not themselves produce
nutrients [52]. Numerous microorganisms, such as nitrogen-fixing soil bacteria
(Azotobacter, Rhizobium), nitrogen-fixing cyanobacteria (Anabaena),
phosphate-solubilizing bacteria (Pseudomonas sp.), and AM fungus, are
frequently utilized as biofertilizers [53]. Similar to this, cellulolytic
microorganisms and phytohormone (auxin)-producing bacteria are also utilized in
the creation of biofertilizers. These microbial formulations are used to speed up
specific microbial processes so that more nutrients are available in
plant-assimilatable forms. A cheap and sustainable source of plant nutrients is
biofertilizers. These are the types of helpful soil microorganisms that have
been cultivated and packaged in the lab in acceptable carriers. A material that
gives a biofertilizer formulation a longer shelf life is known as a carrier.
Examples include peat, lignite powder, vermiculite, clay, talc, rice bran,
seed, charcoal, soil, rock phosphate pellets, paddy straw compost, wheat bran,
and combinations of these materials.
Biopesticides
Using
biotechnology to create synthetic insecticide alternatives to combat insect
pests is also acceptable [54]. To safeguard the plant throughout the crucial
seedling stage, coating formulas for these helpful organisms may be created.
Bacterial and fungal agents like Trichoderma spp., Ampelomyces quisqualis (used
to combat grape powdery mildew), and Bacillus subtilis (used to control plant
diseases) are frequently utilized as second-hand biopesticides [55]. A
microorganism with the agile attribute either directly affects the pathogen as
a biocontrol agent (such as Contans) or creates a chemical during fermentation
that functions as a control (such as Sonata) [56].
The argument for consistent home cooking has made conventional agriculture heavily reliant on pesticides. Growers are investigating new ecologically friendly methods to replace, or at least augment, the current chemical-based processes as a result of the growing clientele and spend on shipboard maintenance. Biopesticides have gainedpopularity as a potential replacement for chemical pesticides. The efficacy of biopesticide bacteria such as Bacillus circulans, Agrobacterium radiobacter, Bacillus pumilus, and Pseudomonas aureofaciens and fungi such as Ampelomyces quisqualis, Fusarium oxysporum, Gliocladium virens, Trichoderma harzianum, and Pythium oligandrum was utilized by many countries for their growth in the field of agriculture for sustainable development [57].
Biotechnology
is becoming increasingly important in the constantly expanding field of
sustainable agriculture. This discipline uses genetic resources from plants,
animals, and microbes to create novel solutions for sustaining agricultural
output while protecting the environment. Sustainable agriculture methods
include a variety of techniques and tactics that address economic and
environmental problems while taking into account the complex interplay of
social, physical, and biological aspects.
Agriculture
has an impact that extends beyond agricultural cultivation to include the
management of critical natural resources such as surface and groundwater,
forests, recreational areas, and wildlife. Climate change is a major global
issue that affects all life on Earth, and sustainable agriculture aims to limit
its consequences. Biodiversity, the foundation of all agricultural plants and
animals, is crucial to agricultural success. Agro ecology, which uses natural
biodiversity to increase crop productivity, is a popular technique. This is
accomplished by cultivating beginning crops, which improves the environmental
conditions for later crops. In essence, sustainable agriculture attempts to
integrate agricultural practices with ecological and economic sustainability,
addressing pressing global concerns while guaranteeing the well-being of both
people and the environment. It is driven by biotechnology and a thorough
understanding of genetic resources.